Horton

RE: Exit walsender before confirming remote flush in logical replication

Hayato Kuroda (Fujitsu) <kuroda.hayato@fujitsu.com>

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From: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>
To: 'Amit Kapila' <amit.kapila16@gmail.com>
Cc: "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>, "sawada.mshk@gmail.com" <sawada.mshk@gmail.com>, "michael@paquier.xyz" <michael@paquier.xyz>, "peter.eisentraut@enterprisedb.com" <peter.eisentraut@enterprisedb.com>, "dilipbalaut@gmail.com" <dilipbalaut@gmail.com>, "andres@anarazel.de" <andres@anarazel.de>, Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Date: 2023-02-08T07:59:09Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Add wal_sender_shutdown_timeout GUC to limit shutdown wait for replication

  2. pg_upgrade: Add --copy option

  3. Prevent possibility of panics during shutdown checkpoint.

  4. Support clean switchover.

Dear Amit,

Thanks for giving comments!

> >
> > 0002:
> >
> > This patch doesn't seem to offer a means to change the default
> > walsender behavior.  We need a subscription option named like
> > "walsender_exit_mode" to do that.
> >
> 
> I don't think at this stage we need a subscription-level option, we
> can extend it later if this is really useful for users. For now, we
> can set this new option when min_apply_delay > 0.

Agreed. I wanted to keep the feature closed for PG16 and then will extend if needed.

> >
> > +ConsumeWalsenderOptions(List *options, WalSndData *data)
> >
> > I wonder if it is the right design to put options for different things
> > into a single list. I rather choose to embed the walsender option in
> > the syntax than needing this function.
> >
> > K_START_REPLICATION opt_slot opt_physical RECPTR opt_timeline
> opt_shutdown_mode
> >
> > K_START_REPLICATION K_SLOTIDENT K_LOGICAL RECPTR
> opt_shutdown_mode plugin_options
> >
> > where opt_shutdown_mode would be like "SHUTDOWN_MODE immediate".
> >
> 
> The other option could have been that we just add it as a
> plugin_option for logical replication but it doesn't seem to match
> with the other plugin options. I think it would be better to have it
> as a separate option something like opt_shutdown_immediate and extend
> the logical replication syntax for now. We can later extend physical
> replication syntax when we want to expose such an option via physical
> replication.

The main intention for us is to shut down logical walsenders. Therefore, same as above,
I want to develop the feature for logical replication once and then try to extend if we want.
TBH I think adding physicalrep support seems not to be so hard,
but I want to keep the patch smaller.

The new patch will be attached soon in another mail.

Best Regards,
Hayato Kuroda
FUJITSU LIMITED